Re: Cleaning surface rust off powdercoating?
[Re: CrazyD]
#922209
02/06/11 02:20 PM
02/06/11 02:20 PM
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Joined: Nov 2007
Posts: 21,832 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,832
Kirkland, Washington
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Quote:
Depending on how bad the surface rust is, perhaps dip a rag in EvapoRust and lay in the affected area. I have had good results on overnight flash rust by just wiping down with a EvapoRust soaked rag. Regardless of treatment, key question is how to protect after rust removal.
Agreed, a liquid rust treat is the way to go in tight areas. I think I would then use paint either spray or maybe dab/brush and let gravity flow it in.
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Re: Cleaning surface rust off powdercoating?
[Re: Pacnorthcuda]
#922210
02/06/11 02:56 PM
02/06/11 02:56 PM
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Joined: Feb 2005
Posts: 28,312 Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
Depending on how bad the surface rust is, perhaps dip a rag in EvapoRust and lay in the affected area. I have had good results on overnight flash rust by just wiping down with a EvapoRust soaked rag. Regardless of treatment, key question is how to protect after rust removal.
Agreed, a liquid rust treat is the way to go in tight areas. I think I would then use paint either spray or maybe dab/brush and let gravity flow it in.
I would think because of this problem that painting would be better for refinishing 2 piece steel wheels than powder coating?
What's everyone think?
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Re: Cleaning surface rust off powdercoating?
[Re: Challenger 1]
#922213
02/06/11 03:14 PM
02/06/11 03:14 PM
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Joined: Feb 2003
Posts: 913
CrazyD
super stock
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super stock
Joined: Feb 2003
Posts: 913
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Re: Cleaning surface rust off powdercoating?
[Re: topside]
#922216
02/06/11 03:43 PM
02/06/11 03:43 PM
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Joined: Jan 2003
Posts: 9,436 Blair County,PA
62maxwgn
master
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master
Joined: Jan 2003
Posts: 9,436
Blair County,PA
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Steve,Muratic acid,it's cheap and will take it right off,however don't let the container sit around opened,the fumes will actually form rust on bare metal that is within ten feet.If you have any rags with it on when you're done get rid of them,better to do them outside (if it's not too cold or the snow isn't too deep ) ,let it on for ten or fifteen minutes and then give them a "GOOD" washing.
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Re: Cleaning surface rust off powdercoating?
[Re: topside]
#922219
02/06/11 08:38 PM
02/06/11 08:38 PM
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Joined: Jan 2007
Posts: 2,212 Minnesota
peabodyracing
top fuel
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top fuel
Joined: Jan 2007
Posts: 2,212
Minnesota
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The problem you're facing is a result of the difficulty of getting powder into the narrow spots between rim and hub. Since powder is applied electrostatically, the powder has a positive charge on it when it leaves the spray gun and is attracted to the metal surface which is grounded, so you have the natural positive wanting to go to ground reaction. Once you have a coat of positively charged powder on the adjacent surfaces there's a natural repelling action. The same problem is experienced in tight corners, channels, etc. If you dwell too long you end up with the coating getting too thick and not looking as good as it should once cured. Often the result is a heavy orange peel look. Anyway, having said all that you end up with unpainted surfaces down there and that's why the rust.
A good applicator will turn the KV down on the spray gun and paint the channel areas 1st to minimize the coverage issue. There are also different tips for the spray gun that can help lay powder in a tight space, but you're still fighting the laws of physics.
There's a secondary issue with painting used steel rims too. Road grime gets lodged into those tight cavities and is just about impossible to clean out. When the painted rim goes into the cure oven, the heat will often cause the contaminates to react and sometimes you'll see little blister like formations down in the crevise. This can also happen during the cure cycle if the powder surface is starting to set up and contaminates 'vent' at the same time, impacting the finished appearance. We try and resist this by using powders that flow for as long as possible during cure.
Acid will definitely attack the surface. At a minimum it will reduce the gloss appreciably and possibly discolor the surface as well. Epoxy powders offer the best chemical resistance, but epoxy resins don't deal well with UV (sunlight) and discolor. Chances are your rims were painted with what's called a TGIC Polyester powder. Great UV resistance, relatively easy to apply, reasonable chemical resistance, but not enough to resist acids or aggressive cleaners any more than the clear coat on your car would.
A few years back we blasted and painted a complete set of side covers for a local Harley enthusiast. He came back later that summer mad as heck because the powder was all streaked. Turned out he'd used EZ Off oven cleaner on the engine. I asked him if he'd use that to clean his gas tank or fenders.
DuPont has a good website on their powders that explains the different chemistries and characteristics very well. Just do a search on DuPont powder coatings to learn more.
It's easier to get liquid paints to go down into the crevise, because there's no charge involved. So you've got a trade off to decide on: the powder is generally more durable than liquid, but you need to make sure your coater gets the rims as clean as possible and works to get powder into those tight spots. Good luck!
Lead, follow or get the hell out of the way
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